Tuning unit for choke coils



Oct. 21, 1941.

M. J. BROWN TUNING UNIT FOR CHOKE COILS Filed Dec. 21, 1939 2 Sheets-Sheet l INVENTOR Mgmrz .IBrOw/Z.

ATTORNEY Patented Oct. 21, 1941 TUNING UNIT FOR CHOKE COILS Myron J. Brown, Wilkinsburg, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application December 21, 1939, Serial No. 310,473

20 Claims.

My invention relates to improvements in the tuning-unit assembly for a carrier-current resonant line choke-coil. These choke-coils consist of relatively large, hollow, air-core inductancecoils which are adapted to be connected in series with a transmission-line to carry the normal power-current, and to choke, or interpose impedance to, the flow of relatively weak, superimposed high-frequency currents through the choke-coil. These choke-coils have one or more so-called tuning-units disposed therein, and electrically connected across the terminals thereof, for the purpose of producing parallel-resonance to one or more carrier-current frequencies. These tuning-units invariably comprise a plurality of capacitors, with a terminahboard for changing the capacitor-connections to alter the tuning, and in my preferred form of embodiment, the tuning-units also embody a variometer which is utilized either as a Vernier-means for tuning between the steps of the capacitor-connections, or, in some instances, as a shunt-connected inductance and auto-transformer for securing special effects such as are described in a copending application of E. T. Hughes and myself, Serial No. 315,384, filed January 24, 194.0, for a Double-frequency resonant choke-coil. As these tuned or resonant choke-coils are designed, in general, for use in the open air, in series with a transmission-line conductor, it is highly desirable that the tuning-unit shall be enclosed in a water-tight casing. Due to the intense magnetic field within the interior of a resonant line choke-coil, the use of metal for enclosing the tuning unit is frequently objectionable because of overheating-troubles due to eddy-currents.

The objects of my invention comprise the redesign of the above-described tuning-unit to incorporate constructional improvements such as the mounting of the electrical parts of the tuning-unit on a chassis or frame consisting of two rods which are supported from internal shoulders which are built into a porcelain cylindrical housing. A further structural improvement relates to the design and mounting of a removable watertight end-cap or cover, the cover preferably having one or more terminals extending therethrough, said terminals terminating, at their inner ends, in flexible pigtails or wires which may be connected to the internal parts of the tuning-unit.

With the foregoing and other objects in View, my invention consists in the parts, apparatus, combinations, methods and systems hereinafter described and claimed, and illustrated in the accompanying drawings, wherein:

Figure 1 is a longitudinal sectional view of a tuningeunit with the end-caps or covers removed, and with portions of the interior construction broken away as being immaterial to an understanding of the important features of my invention;

Fig. 2 is a reduced scale section on the line IIII of Fig. 1;

Fig. 3 is a reduced-scale top plan-view of the cover or end-cap;

Fig. 4 is an elevational view of one end of the tuning-unit assembly, with the end-cap or cover in place, and with parts broken away in section, to better illustrate the construction; and

Fig. 5 is a diagrammatic exploded view illustrating the electrical connections of the tuningunit and the position of the tuning-unit within a line-connected choke-coil.

As shown in Fig. 5, my tuning-unit is designed for mounting within a choke-coil 6 which is illustrated as being supported on a cylindrical, tubular, porcelain supporting-member I, and as being electrically connected in series with a con-- ductor 8 of a transmission-line. The tuningunit consists essentially of a variable capacitance part, which is illustrated as comprising the four capacitors C1, C2, C3 and C4, the terminals of which are connected, through insulated wires 9, to various binding posts It mounted on an insulating terminal-board [2 at one end of the tuning-unit. In my preferred form of construction, the tuningunit also embraces a variometer L which has one or more terminals I3 which are brought through one or more holes M in the terminal-board i2 for adjustable connection to different binding posts -II or groups of binding posts H.

As shown in Fig. 1, the electrical parts of my tuning-unit, that is, the capacitors C1 to C4, the variometer L and the terminal-board I2 are mounted within a long, cylindrical, tubular casing 16 of insulating material, preferably porcelain. It is a distinctive feature of my invention that the electrical parts of the tuning-unit are mounted on a rigid chassis or frame which comprises two long, longitudinally extending rods I! on which all of these electrical parts are mounted, and said rods H are firmly supported, near one end of the tubular porcelain housing I6, by being bolted to an inner shoulder or boss 19 which is either formed integrally with, or firmly united to, the inside of the tubular porcelain housing It. As shown in Fig. 1, the mounting-connection between the rods l1 and the inner porcelain boss 19 is completed by means of two insulating plates 2| and 22 which are disposed on opposite sides of the boss or shoulder l9, and which are clamped between nuts 23 and 24 carried by the rods ll.

One end of the long chassis or frame, which is made essentially of the two long, longitudinally extending rods I7, is thus firmly secured to the essentially integral internal boss IQ of the tubular porcelain housing It. As shown in Fig. 1, for convenience of illustration, this supported end of the chassis-rods I1 is illustrated as being the bottom end, although, in reality, the position of the tubular tuning-unit is almost invariably horizontal, as illustrated in Fig. 5. As shown in Fig. 1, the other end of the chassis-rods ll of the tuning-unit terminate in the terminal-board I2 which also serves as a centering means for abutting against the inner surfaceor bore of the tubular porcelain housing I6. In the particular form illustrated, the edges of the terminal-board l2 are provided with adjustable abutment-screws 25 for making the centering contacts with the inner bore of'the cylindrical housing l6. Between these two ends of the chassis-rods H are mounted the capacitors, such as the capacitors C3 and C4 (the remaining capacitors having been broken away in Fig. 1), and the variometer L, or rather the stator-member 26 of the variometer, the rotor-member 2'! of the variometer being mounted on a shaft 28 which terminates in a tuning-knob 29 on the top of the terminal-board i2.

It will be noted that the internal construction of the chassis I? is such as to avoid the use of metal having a considerable extent in a transverse direction, so as to avoid the development of excessive eddy-currents resulting from the alternating magnetic field which includes magnetic lines of .force extending in the longitudinal direction, and thus tending toproduce eddy-currents in transverse planes.

In the manner shown in Fig. 4, each end of the tubular casing I6 is tightly closed by a removable cover or end-cap 3| having one or more insulatedly bushed terminals 1 32 extending therethrough. In the illustrated embodiment of my i invention, the cover or end-cap BI is made of insulating material, specifically porcelain, having a centrally disposed terminal-rod 32 passing therethrough. At its outer end, the terminal-rod 32 terminates in a metal head or binding post 33 which is separated from the outer end of the insulating cap 3|, by means of a washer 34. The inner end of the terminal-rod 32 is firmly clamped to the inner surface of the insulating cover 3|, with the aid of washers 36 and a nut 31. A water-tight joint is made between the insulating cap 3| and the end of the tubular housing it, by means of a washer 38 which is preferably cemented, at 39, to the cap-member 3|. The inner end of the terminal-rod 32 also carrie a flexible insulated conductor or pigtail H which is utilized to make detachable and adjustable connection to any one or more of the binding posts H of the terminal-board 12 of the tuning-unit.

The end-cap or cover 3| must be securely clamped or pressed against the end of the tubular porcelain housing It, so as to compress the water-tight washer 38 suficiently to make a water-tight joint, and this clamping connection should preferably be effected in a manner such that the end-cap 3| shall be readily removable and so that excessive eddy-currents shall not be generated as a result of the intense longitudi- .nal-ly extending magnetic field resulting fromthe main line-connected choke-coil 6 (Fig. 5) which surrounds the tuning-unit.

As shown in Fig. 4, this clamping connection comprises an encircling metal clamping-ring 43 having split, flanged ends 44 and 45 which are connected by bolts 46, the bolts being insulated at at least one end, as indicated at 41, so as to break the fiow of eddy-currents which would tend to flow circularly around the clamping-ring 43. The clamping-ring is engaged Within a notch or shoulder-abutment 49 which is provided, for the purpose, around the outer surface of the tubular porcelain housing I6. Connected to the clamping ring 43 are a plurality of bolts 5| which engage a, metallic clamping-casting 52 which fits over the end of the end-cap or cover 3|, so as to clamp the end-cover 3| firmly in place, on the end of the tubular insulating housing It. As shown in Fig. 3, one end of the clamping-casting 52 is split, as indicated at 53, in order to prevent eddy-current fiow.

From the foregoing explanation, it will be seen that I have provided a simple, strong, internal chassis-construction, and external water-proof design, for my improved tuning-unit.

Electrically, as illustrated in Fig. 5, the unit is connected between the terminals of the line-connected choke-coil 6, by means of connectors 55 and 56. The connector 55 is connected to the terminal-cap 33 of the end-cover 3| at the end of the tuning-unit which has the flexible pigtail 4| which is connected to the selected terminals H of the terminal-board 2 of the capacitors C1 to C4. The other line-connector 55 is similarly connected to the other end-cap 3| at the other end of the tuning-unit, as shown in Fig. 5, this end-cap 3| having an internal pigtail 4| which is connected to one of the rods ll of the tuning-element chassis, one terminal of the variometer being grounded or connected on this same rod IT, as indicated at 51. The illustrated electrical connection is indicated only by way of illustration, as I am not limited to this particular form of connection or use of the tuning-element.

While I have illustrated my invention in a single form of embodiment which is at present preferred by me, I wish it to be understood that I am not altogether limited to this particular form of embodiment, as various changes may be made by those skilled in the art without departing from the essential features of my invention, particularly in its broader aspects. I desire, therefore, that the appended claims shall be accorded the broadest construction consistent with their language and the prior art.

I claim as my invention:

1, The combination, with a relatively heavyduty, alternating-current, large-diameter lineconnected choke-coil, of a relatively light-current tuning-unit disposed within said line-connected choke-coil, said tuning-unit comprising an open-ended tubular insulating casing, a readily removable water-tight cover for an open end of said tubular insulating casing, a variable 'capacitive impedance-device and means for adjusting the same disposed within said casing, with the adjustment-means accessible at the aforesaid open end, -a chassis for supporting said impedance-device and said adjustment-means, said chassis comprising two longitudinally extending rods, and internal shoulder-means carried Icy-said tubular insulating casing for supporting'ly engaging said rods independently of said cover.

2. The combination, with a relatively heavyduty, alternating-current, large-diameter lineconnected choke-coil, of a relatively light-current tuning-unit disposed within said line-connected choke-coil, said tuning-unit comprising an openended tubular insulating casing having both ends open, a variable capacitive impedance-device and means for adjusting the same disposed within said casing, a separate, readily removable Water-tight cover of insulating material for each open end of said casing, each cover comprising an insulatingly bushed terminal extending therethrough, a flexible connector for connecting the inner end of said terminal to said impedance-device, and fastening-means for each cover, each fasteningmeans comprising a split metallic band encircling said casing, the casing having a shoulder-abutment for retaining said band, said band including means for tightening it around the casing and for insulatingly blocking the flow of induced currents around the casing, and disengageable fastening-means for tightly drawing the associated end-cover to said band.

3. The combination, with a relatively heavyduty, alternating-current, large-diameter lineconnected choke-coil, of a relatively light-current tuning-unit disposed within said line-connected choke-coil, said tuning-unit comprising an openended tubular insulating casing, a variable capacitive impedance-device and means for adjusting the same disposed within said casing, a readily removable water-tight cover of insulating material for an open end of said casing, the adjustment-means being accessible at the aforesaid open end, and fastening-means for said cover, said fastening-means comprising a split metallic band encircling said casing, the casing having a shoulder-abutment for retaining said band, said band including means for tightening it around the casing and for insulatingly blocking the flow of induced currents around the casing, a metal clamping-member fitting over said cover, said metal clamping-member being split, and disengageable fastening-means for tightly drawing said clamping-member to said band.

4. The combination, with a relatively heavyduty, alternating-current, large-diameter lineconnected choke coil, of a relatively light-current tuning-unit disposed within said line-connected chokecoil, said tuning-unit comprising an open-ended tubular insulating casing; a readiiy removable water-tight cover for an open end of said tubular insulating casing; a variable capacitive impedance-device, a variable inductive impedance-device and means for adjusting the same disposed within said casing, with the ad-- justment-means accessible at the aforesaid open end; a chassis for supporting said impedancedevices and the internal parts of said adjustmentmeans, said chassis comprising two longitudinally extending rods; and internal shoulder-means carried by said tubular insulating casing for supportingly engaging said rods independently of said cover.

5. A tuning-unit comprising an open-ended tubular insulating casing, a readily removable water-tight cover for an open end of said tubular insulating casing, a variable capacitive impedance-device and means for adjusting the same disposed within said casing, with the adjustmentmeans accessible at the aforesaid open end, a chassis for supporting said impedance-device and said adjustment-means, said chassis comprising two longitudinally extending rods, and internal shoulder-means carried by said tubular insulating casing for supportingly engaging said rods.

6. A tuning-unit comprising an open-ended tubular insulating casing having both ends open, a variable capacitive impedance-device and means for adjusting the same disposed within said casing, a separate, readily removable water-tight cover of insulating material for each open end of said casing, each cover comprising an insulatingly bushed terminal extending therethrough, a flexible connector for connecting the inner end of said terminal to said impedance-device, and fastening-means for each cover, each fasteningmeans comprising a split metallic band encircling said casing, the casing having a shoulderabutment for retaining said band, said band including means for tightening it around the casing and for insulatingly blocking the flow of induced currents around the casing, and disengageable fastening-means for tightly drawing the associated end-cover to said band.

'7. A tuning-unit comprising an open-ended tubular insulating casing, a variable capacitive impedance-device and means for adjusting the same disposed within said casing, a readily removable water-tight cover of insulating material for an open end of said casing, the adjustmentmeans being accessible at the aforesaid open end, and fastening-means for said cover, said fastening-means comprising a split metallic band encircling said casing, the casing having a shoulderabutment for retaining said band, said band including means for tightening it around the casing and for insulatingly blocking the flow of induced currents around the casing, a metal clampingmember fitting over said cover, said metal clamping-member being split, and disengageable fastening-means for tightly drawing said clampingmember to said band.

8. A tuning-unit comprising an open-ended tubular insulating casing; a readily removable water-tight cover for an open end of said tubular insulating casing; a variable capacitive impedance-device, a variable inductive impedance-device and means for adjusting the same disposed within said casing, with the adjustment-means accessible at the aforesaid open end; a chassis for supporting said impedance-devices and said adjustment-means, said chassis comprising two longitudinally extending rods; and internal shoulder-means carried by said tubular insulating casing for supportingly engaging said rods independently of said cover.

9. An open-ended tubular insulating casing, a readily removable water-tight cover for an open end of said tubular insulating casing, an adjustment-means accessible at the aforesaid open end, a chassis comprising two longitudinally extending rods, and internal shoulder-means carried by said tubular insulating casing for supportingly engaging said rods.

10. An open-ended tubular insulating casing having both ends open, a separate, readily removable water-tight cover of insulating material for each open end of said casing, each cover comprising an insulatingly bushed terminal extending therethrough, and fastening-means for each cover, each fastening-means comprising a split metallic band encircling said casing, the casing having a shoulder-abutment for retaining said band, said band including means for tightening it around the casing and for insulatingly blocking the flow of induced currents around the casing, and disengageable fastening' means for tightly drawing the associated end-cover to said band.

11. An open-ended tubular insulating casing, a readily removable water-tight cover of insulating materialfor an open end :of said casing, an adjustment-means accessible at the aforesaid open end, and fastening-means for said cover, said fastening-means comprising a split metallic band encircling said casing, the casing having a shoulder-abutment for retaining said band, said band including means for tightening it around the casing and forinsulatingly blocking the flow of induced currents around the casing, a metal clamping-member fitting over said cover, said metal clamping-member being split, and disengageablefastening-means for tightly drawing said clamping-member to said band.

12. An open-ended tubular insulatingcasing, a readily removable water-tight cover for an open end of said tubular insulating casing, a chassis comprising two longitudinally extending rods, and internal shoulder-means carried by said tubular insulating casing for supportingly engaging said rods independently of said cover.

'13. An open-ended tubular insulating casing, a readily removable water-tight cover of insulating material for an open end of said casing,

, and fastening-means for said cover, said fastening-means comprising a split metallic band encircling said casing, the casing having a shoulder-abutment for retaining said band, said band including means for tightening it around the easing and for insulatingly blocking the flow of induced currents around the casing, a metal clamping-member fitting over said cover, said metal clamping-member being split, and disengflgeable fastening-means for tightly drawing said clamping-member to said band.

14. The combination, with a relatively heavyduty, alternating-current, large-diameter, aircore, outdoor choke-coil, of a relatively light-current adjustable unit disposed within said chokecoil, said adjustable unit comprising an openended tubular insulating casing, a readily removable water-tight cover of insulating material for an open end of said tubular insulating casing,,a variable device and means for adjusting the same disposed within said casing, with the adjustment-means accessible at the aforesaid open end, .a chassis for supporting-said variable device and said adjustment-means, said chassis comprising two longitudinally extending rods, and internal shoulder-means carried by said tubular insulating casing for supportingly engaging said rods independently of said cover.

15. The combination, with a relatively heavyduty, alternating-current, large-diameter, .aircore, outdoor choke-coil, of a relatively slight-current vadjusting unit disposed within said .chokecoil, said adjusting .unit comprising an openended tubular insulating casing having both ends open, a variable electrical device and means for adjusting the same disposed within said casing, .a separate, readily removable water-tight cover of insulating material for each openend .Ofsaid casing, each cover comprising an insulatingly hushed terminal extending therethrough, a flexible connector iorconnecting the inner end of said terminal to said electrical device, and fasteningmeans for eac'hcover, each fastening-means comprising a-split metallic band encircling said .casing, the casing having a shoulder-abutment for retaining said band, said band including means for tightening .it around the casing and for insulatingly blocking the flow of induced currents around the casing, and disengageablefasteningmeans iortightly drawing the associated endcover to said'band.

16. Ifhe combination, with a relatively heavyduty, alternating-current, large-diameter, aircore, outdoor choke-coil, of a relatively light-current adjustable unit disposed within said chokecoil, said adjustable unit com-prising an openended tubular insulating casing, a variable electrical device and means for adjusting the same disposed within said casing, a readily removable water-tight cover of insulating material for an open end of said casing, the adjustment-means being accessible at the aforesaid open end, and fastening-means for said cover, said fasteningmeans comprising a split metallic band encircling said casing, the casing having a shoulderabutment for retaining said band, said band including means for tightening it around the casing and for insulatingly blocking the flow of induced currents around the casing, a metal clamping-member fitting over said cover, said metal clamping-member being split, and disengageable fastening-means for tightly drawing said clamping-member to said band.

17. The combination, with a relatively heavy- .dut alternating-current, large-diameter, aircore, outdoor choke-coil, of a relatively light-current adjustable unit disposed within said choke- .coil, said adjustable unit comprising an openended tubular insulating casing; a readily removable watertight cover of insulating material for an open end'of said tubular insulating casing; a plurality of variable electrical devices and means for adjusting the same disposed within said'casing, with the adjustment-means accessible at the aforesaid open end; a chassis for supporting said electrical devices and the internal parts ,of said adjustment-means, said chassis comprising two longitudinally extending rods; and internal shoulder-means carried by said tubular insulating casing for supportingly engaging said rods independently of said cover.

18. An open-ended tubular insulating casing, a readily removable water-tight cover for an .open end of said tubular insulating casing, an adjustment-means accessible at the aforesaid open end, a chassis comprising two longitudinally extending rods, internal shoulder-means carried by said tubular insulating casing for supportingly engaging said rods, and an adjustable device mounted on said chassis within the casing and operatively connected to said externally accessible adjustment-means.

v 19. An open-ended tubular insulating casing, a readily removable Water-tight cover of insulating material for an open end of said casing, an adjustable device within the casing, an adjustmentemeans therefor accessible at the aforesaid open endand fastening-means for said cover, said fastening-means comprising asplit metallic bandencircling said casing, the casing having a shoulder-abutment for retaining said band, said band including means for tightening it around the casing and for insulatingly blocking the flow of induced currents around the casing, a metal clamping-member fitting over said cover, said metal clamping-member being split, and disengageable iastening ineans for tightly drawing said clamping-member to said band.

20. An open-ended tubular insulating casing, a chassis comprising two longitudinally extending rods, and internal shoulder-means carried by said tubular insulating casing for supportingly engaging said rods.

'MYRON J. BROWN. 

